Magnetic correlations in amorphous Fe-Zr alloys

Abstract

Results of high-resolution small-angle neutron scattering (SANS) studies on amorphous alloys of composition FexZr100−x, x=90, 91, 92, show that ferromagnetic correlations exist below Tc, but that conventional long-range order is destroyed by competing exchange interactions. The transition temperatures drop with increasing iron concentration (Tc ≊226 K for Fe90Zr10 down to Tc ≊175 K for Fe92Zr8). Data taken at very low Q (0.008 Å−1<Q<0.02 Å−1) provide evidence of relatively large (≊200–≊400 Å) static spin clusters which do not disorder at Tc. Superposed on this is an ordering with a second shorter length scale which shows a cusp (not divergent) at the bulk Tc. The data were fitted to a combination of a Lorentzian and a power of a Lorentzian, the latter of which represents scattering from clusters with a Maxwellian distribution of sizes.